JP5620794B2 - piston ring - Google Patents

Description

  The present invention relates to a low friction piston ring for an internal combustion engine that slides on a cylinder liner or an inner wall surface of a cylinder.

Environmental issues such as global warming have been greatly highlighted on a global scale, and the development of fuel efficiency improvement technology for internal combustion engines to reduce CO _{2 in} the atmosphere has become a major issue. Reduction of the friction loss of the sliding member is required. In view of this, in recent years, the development of sliding member materials, surface treatment, and modification technologies that are excellent in wear resistance and seizure resistance and that can maximize the effect of reducing frictional force have been developed. It is being advanced.

  In order to improve the energy efficiency of an apparatus using a cylinder, such as improvement of fuel consumption of an internal combustion engine, reduction of friction loss is effective. In particular, it is effective to reduce friction between the outer peripheral sliding surface of the piston ring that reciprocates and the cylinder liner or the inner wall surface of the cylinder. As a means for reducing the frictional force between the piston ring and the cylinder liner, it is conceivable to lower the tension of the piston ring. However, when the tension of the piston ring is lowered, there is a problem that the sealing performance is lowered and the consumption amount of the lubricating oil is increased.

  Under such circumstances, various studies have been made on piston rings that can reduce frictional force while suppressing the consumption of lubricating oil. Patent Document 1 discloses that fine dimples are formed on the outer peripheral sliding surface. An improved piston ring has been proposed. In this proposal, dimples are formed on the outer peripheral sliding surface of the piston ring to reduce the contact area between the outer peripheral sliding surface of the piston ring and the inner wall surface of the cylinder liner, thereby reducing the frictional force.

  Patent Document 2 proposes a piston ring in which a large number of grooves are formed on the outer peripheral surface and a piston ring in which a plurality of dimples are formed. In this proposal, grooves and dimples are formed on the outer peripheral surface to improve the sliding contact with the inner wall surface of the cylinder liner and reduce wear.

JP 2004-60873 A JP 2010-38295 A

  However, the piston ring proposed in Patent Document 1 does not pay attention to how much the dimples are formed and the position of the dimples. In the piston ring proposed in Patent Document 2, However, it is only disclosed that the number of dimples to be formed is to reduce the number of dimples on the lower surface side than the upper surface side, and the area ratio, size, etc. of other dimples have been studied. It has not been. For example, when dimples are excessively formed on the outer peripheral sliding surface, the frictional force, gas seal, and oil seal functions are lowered, and there is a high possibility that problems such as scuffing will occur.

  The present invention has been made in view of such circumstances, has excellent sliding characteristics such as scuff resistance, can reduce the coefficient of friction to meet the demand for low friction of an internal combustion engine, and is a gas seal. The main object is to provide a piston ring that does not deteriorate the oil seal function.

The present invention for solving the above problems is a piston ring for an internal combustion engine that is mounted in a ring groove of a piston and slides against a cylinder liner or an inner wall surface of the cylinder, A plurality of minute recesses are formed in the barrel width region of the ring, and the area of the recess non-formation region where the recess is not formed in the barrel width region is the total area of the barrel width region before the recess formation. It is within a range of 20 to 85% when 100% is set, and the concave portion non-formation region exists in all of the axial cut surfaces of the barrel width region, and the piston ring is a ring groove of the piston. In the state where the piston is incorporated in the cylinder, when the straight line passing through the central axis of the cylinder and the outer peripheral end of the joint portion is used as a reference line, the central axis is The said barrel width region ranging angle of less than 1 ° with the reference line on the heart, wherein the concave portion is not formed.

  Moreover, the hard film | membrane may be formed in the said recessed part non-formation area | region.

  Further, the recess may be formed so as not to straddle the lower end portion in the axial direction of the outer peripheral sliding surface, and when the lower end portion of the piston ring is chamfered, the chamfered portion is formed. The recess may be formed so as not to straddle.

  According to the piston ring of the present invention, since the concave portion is formed in the barrel width region so that the area of the non-recessed region is within the above range, the requirement for low friction can be sufficiently satisfied. Further, since there is a recess-unformed region on all the axial cut surfaces of the barrel width region, the gas seal and oil seal functions are not lowered in the same manner.

It is a schematic sectional drawing for demonstrating the barrel width area | region of the piston ring of this invention. It is the expansion perspective view seen from the outer periphery of the piston ring of the joint part vicinity in the piston ring of this invention. It is a general | schematic expanded view seen from the outer periphery of the piston ring of the piston ring of this invention near the abutment part. It is a general | schematic expanded view seen from the outer periphery of the piston ring of the piston ring of this invention near the abutment part. FIG. 5A is a schematic diagram showing the relationship between the cylinder center axis O and the center angle, and FIG. 5B shows that a recess is formed in the barrel width region within a range of less than 1 ° of the center angle. It is a general | schematic expanded view seen from the outer periphery of the piston ring of the joint part vicinity which shows a non-piston ring. It is the general | schematic expanded view seen from the outer periphery of the piston ring of the piston ring vicinity of the present invention in which the recessed part was formed in the whole surface of the outer periphery sliding surface. It is a general | schematic expanded view which shows the lower end part vicinity seen from the outer periphery of the piston ring of the piston ring of this invention. It is a general | schematic expanded view which shows the example of the shape of the recessed part formed in the piston ring of this invention. It is the general | schematic expanded view and schematic sectional drawing explaining the dimension position of the recessed part formed in the cylinder of this invention. It is the schematic which shows the opening part of the masking board used in the Example of this invention. It is a schematic sectional drawing which shows the structure of the apparatus used in order to measure the reciprocating friction in the Example of this invention. It is a graph which shows the measurement result in the Example of this invention. It is a graph which shows the measurement result in the Example of this invention.

  A piston ring according to the present invention is a piston ring for an internal combustion engine that is mounted in a ring groove of a piston and slides on a cylinder liner or an inner wall surface of the cylinder, and of the outer peripheral sliding surface of the piston ring, the barrel width of the piston ring A plurality of minute recesses are formed in the region, and the area of the recess non-formation region in which no recess is formed in the barrel width region is 20 when the total area of the barrel width region before the recess formation is 100%. It is within a range of ˜85%, and there is a recess non-formation region in all of the axial cut surfaces of the barrel width region.

  The barrel width region of the piston ring in the present invention means the symbol h8 shown in JIS B 8032-6 (1998). Further, in the case of barrel face rectangular ring as shown in FIG. 1, the entire outer peripheral sliding surface 200 does not become the barrel width region 100. It becomes the barrel width region 100. FIG. 1 is a schematic cross-sectional view for explaining a barrel width region 100 of the piston ring 10. Hereinafter, the description will focus on a piston ring that has a barrel-shaped outer peripheral sliding surface 200 and whose upper and lower ends in the axial direction of the outer peripheral sliding surface are chamfered. However, the present invention is limited to this embodiment. is not.

  The material of the piston ring body of the present invention is not particularly limited, and any material can be used. For example, steel (steel material) can be mainly used as the material, and as stainless steel, SUS440, SUS440B, SUS410, SUS420, SUS304 or the like, or 8Cr steel, 10Cr steel, SWOSC-V, SWRH material, etc. Can be used. Moreover, you may use the steel material which performed the nitriding process. As a kind of piston ring, not only a top ring that functions as a so-called pressure ring but also a second ring that is the same pressure ring can be used.

  Next, the recessed part 3 formed in the barrel width area | region 100 of the piston ring of this invention with reference to FIGS. 2 is an enlarged perspective view showing an example of the vicinity of the joint when the piston ring of the present invention is viewed from the outer periphery of the piston ring, and FIGS. 3 and 4 show the piston ring of the present invention in the outer periphery of the piston ring. It is a general | schematic expanded view which shows an example of the joint part vicinity when it sees.

  As shown in FIG. 2, a plurality of minute recesses 3 are formed in the barrel width region 100 of the piston ring 10 of the present invention. With this configuration, the reciprocating frictional force between the piston ring 10 and the cylinder liner or the inner wall surface of the cylinder can be reduced.

  Furthermore, in the piston ring 10 of the present invention, the area of the non-recessed region 4 where the recess 3 is not formed in the barrel width region 100 is 20 to 20% when the total area of the barrel width region before forming the recess is 100%. Within the range of 85%, the recess non-formation region 4 exists in all of the cut surfaces in the ring axis direction of the barrel width region 100. In addition, the recessed part non-formation area | region 4 is an area | region of the part in which the recessed part 3 is not formed in the barrel width area | region 100. FIG.

  According to the piston ring 10 of the present invention having the above-described features, it is possible to prevent problems such as scuffing while maintaining the effect of reducing the reciprocating frictional force between the cylinder liner and the inner wall surface of the cylinder. In addition, when the area of the recessed part non-formation area | region 4 is less than 20% (when the ratio which a recessed part occupies is large), the surface pressure of a sliding part will become remarkably high and a frictional force will be because a contact area is too small. It will increase. On the other hand, when the area of the recess non-formation region 4 exceeds 85% (when the ratio of the recesses is small), the effect of forming the recesses 3 cannot be sufficiently obtained. Moreover, when the recessed part non-formation area | region 4 does not exist in all the ring axial direction cut surfaces of the barrel width area | region 100, a sealing performance (airtightness) will fall remarkably.

  The piston ring 10 of the present invention has an essential requirement that the recess-unformed region 4 be present on all the cutting surfaces in the ring axial direction of the barrel width region 100, and the barrel width is set so as to satisfy this requirement. In the region 100, a plurality of recesses 3 are formed.

  The method for satisfying the above requirements is not particularly limited. For example, as shown in FIG. 3A, the length in the ring axis direction is longer than the length in the ring axis direction (L1) of the barrel width region in the barrel width region 100. When the short recess 3 is formed, the recess non-formation region 4 can be present on the ring axis direction cut surface of the barrel width region 100 regardless of the formation position of the recess 3.

  FIG. 3A is an example of a piston ring in which the concave portion 3 having a shorter length in the ring axis direction than the length (L1) in the ring width direction of the barrel width region is formed on the entire surface in the barrel width region 100. However, the present invention is not limited to this configuration. For example, as shown in FIG. 3B, the recesses 3 can be formed in a concentrated manner in a region near the barrel apex in the barrel width region 100 within a range that satisfies the above requirements. Further, if the concave portion 3 is formed in the barrel width region 100 within a range that satisfies the above requirements, as shown in FIG. 3C, not only the barrel width region 100 but also the entire outer peripheral sliding surface 200. A recess 3 can also be formed in

  On the other hand, when the concave portion 3b having a longer ring axis direction length than the barrel width region 100 length is formed in the barrel width region 100, as shown in FIG. However, it penetrates by one recessed part 3b, and it becomes impossible to make the recessed part non-formation area | region 4 exist in the ring-axis direction cutting surface of the barrel width area | region 100, and a sealing performance falls remarkably.

  The number of recesses formed in the barrel width region 100, the shape of the recesses, and the like are not particularly limited, but at least the area of the recess non-formed region 4 where the recesses 3 of the barrel width region 100 are not formed is It is necessary to adjust the number and shape of the recesses so that they are within a range of 20 to 85% of the total area of the barrel width region when not formed.

  Moreover, although it changes with engines, it is preferable that the recessed part 3 is formed in the range of 8-50% from the barrel top with respect to a barrel width, and the inside of the range of 8-25% is more preferable. By forming the recess 3 at a position close to the top of the barrel, it is possible to sufficiently reduce the frictional force during the initial sliding, and to control the sealing function between the outer peripheral sliding surface of the piston ring and the inner wall surface of the cylinder. it can. The barrel apex is a central portion in the ring axis direction in a symmetric barrel, and a portion having a maximum radial length in the ring axis direction in an eccentric barrel.

  Further, as shown in FIGS. 5A and 5B, the recess 3 is formed so that the piston ring is mounted on the piston and the piston is incorporated in the cylinder, and the outer peripheral end of the center axis (O) of the cylinder and the joint portion. When the straight line passing through the section (S) is the reference line (P), the barrel width region (100Q) in the range where the angle between the reference line (P) and the center axis (O) is less than 1 ° The recess 3 is preferably not formed. By not forming the recess 3 in the barrel width region (100Q) within this range, the possibility of problems such as scuffing due to an excessive increase in surface pressure at the joint can be reduced. FIG. 5A is a schematic diagram showing the relationship between the cylinder center axis (O), the reference line (P), and the angle formed by the reference line (P), and FIG. When the straight line passing through the central axis (O) and the outer peripheral end (S) of the joint portion is defined as the reference line (P), the angle between the central axis (O) and the reference line (P) is less than 1 °. It is a general | schematic expansion | deployment figure when seeing the abutment part vicinity which shows the piston ring in which the recessed part 3 is not formed in the barrel width area | region (100Q) of the range of from the piston ring outer periphery.

  Further, when the piston slides, combustion pressure is applied from the upper surface of the piston ring, and stress concentration tends to occur on the lower surface side of the piston ring. Then, as shown in FIG. 7C, when the concave portion 3 is formed so as to straddle the lower end portion in the axial direction of the outer peripheral sliding surface, the piston ring is easily broken from the concave portion 3 as a starting point. Considering such points, it is preferable that the recess 3 is not formed so as to straddle the lower end in the axial direction of the outer peripheral sliding surface as shown in FIG. Further, when the chamfered portion is formed so as to contact the lower end portion of the outer peripheral sliding surface as shown in FIG. 7D, when the concave portion 3 is formed so as to straddle the chamfered portion, The piston ring is easily broken from the recess 3 as a starting point. Considering such points, it is preferable that the recess 3 is not formed so as to straddle the chamfered portion as shown in FIG. 7A to 7D are schematic development views showing a recess formed in the vicinity of the lower end portion in the axial direction of the outer peripheral sliding surface of the piston ring.

  Moreover, in this aspect, the front shape (surface developed in the circumferential direction of the piston ring) of the concave portion formed in the barrel width region of the piston ring is not particularly limited, and is appropriately adjusted according to the arrangement of the concave portion and the like. be able to. For example, as illustrated in FIGS. 8A to 8J, a concave portion having a shape constituted by a straight line and / or a curved line can be formed. The concave portions may be horizontally long as shown in FIGS. 8A to 8C, vertically long as shown in FIGS. 8D to 8G, or vertically as shown in FIGS. 8H to 8J. A shape with a substantially equal ratio of width to width may be used.

  The average circumferential length of the recesses is preferably in the range of 0.01 mm to 5 mm, and particularly preferably in the range of 0.01 mm to 0.3 mm. When the circumferential average length is less than this range, the effect of forming the recess may not be sufficiently obtained. On the other hand, when the circumferential average length exceeds this range, problems such as deformation of the piston ring may occur.

  In this aspect, the average radial length of the recesses is preferably in the range of 0.1 μm to 100 μm, and more preferably in the range of 0.5 μm to 30 μm. If the average radial length of the recess is less than this range, the effect of forming the recess may not be sufficiently obtained. On the other hand, if the radial average length exceeds this range, processing is difficult, and problems such as the need to increase the radial average length of the piston ring (thickening the wall thickness) occur. There is a case. In addition, it is necessary to set the radial direction average length of a recessed part suitably so that a recessed part inner peripheral surface may not protrude from a barrel width area | region.

  In this embodiment, the average length in the circumferential direction between adjacent recesses (the average length in the circumferential direction of the non-recessed region) is preferably in the range of 0.1 mm to 15 mm, and in the range of 0.3 mm to 5 mm. Is particularly preferred. If the average length in the circumferential direction between adjacent recesses (the average length in the circumferential direction of the non-recessed area) is less than this range, there is a possibility that the piston ring and the inner wall surface of the cylinder cannot slide stably. is there. On the other hand, when it exceeds this range, the effect of forming the recess may not be sufficiently obtained.

  In addition, each average length of the recessed part mentioned in this aspect shall mean the average length of each location illustrated in FIG. FIG. 9A is a schematic development view showing the axial direction of the piston ring in the barrel width region in the vertical direction of the drawing. FIG. 9B is a schematic cross-sectional view in the circumferential direction of the barrel width region. The axial average length of the concave portion is an average length of the concave portion in the piston ring axial direction as illustrated in FIG. 9A.

  Moreover, the circumferential direction average length of the said recessed part is an average of the length of the recessed part in a cylinder circumferential direction so that it may illustrate in Fig.9 (a). As illustrated in FIG. 9B, the average length in the circumferential direction of the recess means an average length in the opening region formed by the recess.

  Moreover, the radial direction average length of the said recessed part is the average of the length from the bottom face of a recessed part to a recessed part non-formation area | region so that it may illustrate in FIG.9 (b). Moreover, the circumferential direction average length between the said recessed parts (average length of a recessed part non-formation area | region) is the average of the space | interval of an adjacent recessed part so that it may illustrate in FIG.9 (a) and (b).

  In this aspect, from the viewpoint of reducing the reciprocating frictional force between the piston ring and the inner wall surface of the cylinder liner, the ten-point average roughness (Rz) of the non-recessed region 4 is preferably 3.2 μm or less. Particularly preferably, it is 1.6 μm or less. The ten-point average roughness Rz is defined in JIS B0601-1994.

(Method for forming recesses)
The method for forming the recess formed in the barrel width region of this aspect is not particularly limited, and any method can be adopted as long as the recess satisfying the above-described conditions can be formed.

  For example, a blasting method for forming recesses by spraying abrasive grains after masking, a method for forming recesses by masking and then applying to a corrosive solution, and a relief liquid instead of ink in letterpress printing Corrosion processing method using can be adopted.

  Moreover, after forming a hard film in the barrel width area | region of a piston ring by hard film processes, such as various PVD methods and CVD method, the method of forming a recessed part with said method is also employable. According to this method, since the hard film is formed in the recess non-formation region 4, the wear resistance of the recess non-formation region 4 can be improved. Also, a PVD film or CVD film is formed as a hard film, or a DLC (Diamond Like Carbon) film is formed on the PVD film or CVD film, and then a recess is formed by the above method. May be. Since the DLC film has low friction, the frictional force can be further reduced.

  Further, in the piston ring of this aspect, it is only necessary that a concave portion is finally formed in the barrel width region, and it is not always necessary to use the concave portion for removing the piston ring surface in the manufacturing process. By forming a convex portion (recessed portion non-forming region 4) on the surface, a portion where the convex portion (recessed portion non-forming region 4) is not formed as a result may be set as a concave portion. In this case, specifically, after predetermined masking, a method of forming a hard film as a convex portion (a concave portion non-formation region 4) by various PVD methods or CVD methods can be used.

(Surface treatment of non-recessed area)
Moreover, when the recessed part 3 is formed in the barrel width area | region 100 as demonstrated above, since piston ring outer peripheral surface pressure increases, abrasion of a piston ring outer peripheral surface will be accelerated | stimulated. Further, the frictional force tends to increase at the top dead center stop position and the bottom dead center stop position when the piston ring reciprocates. In consideration of such points, surface treatment for reducing the frictional force at the outer peripheral surface of the piston ring and reducing the frictional force at the top dead center stop position and the bottom dead center stop position is provided in the non-recessed region 4. It is preferable that it is given. Examples of such surface treatment include a method of forming a hard coating, a low friction DLC (diamond-like carbon) coating or a highly wear resistant PVD coating on the non-recessed region 4. be able to. In particular, in the present invention, a surface treatment in which a PVD film such as Cr—Ni or Ti—Ni is formed on the non-recessed region 4 and a DLC film is formed on the PVD film is preferable. In the barrel width region 100, the sliding surface gradually expands in the radial direction as the piston slides. Therefore, it is preferable that the outer peripheral sliding surface 200 is also subjected to the above surface treatment. As described above, when forming a recess after forming a hard coating in the barrel width region of the piston ring, or when forming a projection (depressed portion non-forming region 4) with a hard coating, It is unnecessary.

(Surface treatment of the inner peripheral surface of the recess)
Also, the lubricating oil is held on the inner peripheral surface of the recess during sliding. Here, when the lubricating oil retained on the inner peripheral surface of the recess is oxidized and deteriorated, soot containing carbon as a main component is generated, and the generated soot adheres to the inner peripheral surface of the recess, and then the inner peripheral surface of the recess From the soot adhering to the starting point, soot gradually accumulates in the recess. When crevice clogs due to accumulation of soot, the contact area between the piston ring and the cylinder liner increases, and the effect of reducing the reciprocating friction exhibited by forming the crevice is maintained over a long period of time. I can't do that.

  Considering such points, it is preferable that the inner surface of the recess is subjected to a surface treatment for preventing the lubricating oil from being retained for a long period of time. Examples of such a surface treatment include a method of coating a resin having oil repellency in the recess and a phosphate film treatment for forming a phosphate film on the surface of the recess. The phosphate film treatment refers to a chemical conversion treatment that chemically forms a phosphate film on the surface of a metal using a phosphate treatment solution. Moreover, as resin which has oil repellency, a fluororesin etc. can be mentioned, for example.

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.

  A piston ring having a recess formed in the barrel width region was processed by the following method.

<Processing of piston ring>
(Preparation of piston ring before processing)
The piston ring before the recessed part process which has the following properties was prepared.
Material: SUS410J1
Shape: Barrel shape Outer diameter (D): 95.4mm
Axial height (h1): 2 mm
Radial width (a1): 2.55mm
Top and bottom chamfering: 0.2mm
Barrel width region 100 axial length: 1.2 mm

  The piston ring was subjected to gas nitriding at 550 ° C. for 5 hours, and then the outer peripheral sliding surface was coated with a Cr—B—N film of 30 μm. The Vickers hardness was 1800 Hv (0.1).

(Preparation of masking plate)
Masking plates 1 to 7 having hexagonal openings shown in FIG. 10A having the dimensions shown in Table 1 below were prepared. The used masking plates 1 to 7 are made of S45C and have a thickness of 0.1 mm. In the masking plates 1 to 7, the piston ring is mounted in the ring groove of the piston, and in a state where the piston is incorporated in the cylinder, a straight line passing through the center axis of the cylinder and the outer peripheral end of the joint portion is used as a reference line. In this case, the opening is provided except for the position corresponding to the barrel width region in which the angle formed with the reference line around the central axis is less than 5 °.

(Formation of recesses)
(1) A workpiece was prepared in which the piston ring before processing the outer peripheral sliding surface prepared above was held in a cylinder alternately with the spacer ring, and the masking plate 1 was wound around the outer periphery of the piston ring. Next, a holding ring for fixing the masking plate so as not to move was wound around the outer periphery of the masking plate. A masking plate can be set between the spacer ring and the holding ring.
(2) The workpiece was set on a turntable of a blasting machine, and blasting was performed from the masking plate side under the following processing conditions to form a recess.
<Processing conditions>
Abrasive: Alumina injection pressure: 0.1 MPa
Work rotation speed: 298rpm
Distance between gun and workpiece: 40mm
Gun vertical feed speed: 164mm / min
Gun injection port diameter: φ8mm
Gun reciprocation frequency: 3 reciprocation injection time: 8 min
(3) The workpiece was removed from the turntable, and then the masking plate and the piston ring after forming the recess were removed from the cylinder. A piston ring having a recess formed using the masking plate 1 was used as the piston ring of Example 1.
(4) The above operations (1) to (3) were similarly performed on the masking plates 2 to 7. The piston rings in which the recesses were formed using the masking plates 2 to 4 were used as the piston rings of Examples 2 to 4, respectively. The piston ring in which the recess was not processed was used as the piston ring of Comparative Example 1. Moreover, the piston ring in which the recessed part was formed using the masking plates 5-7 was made into the piston ring of Comparative Examples 2-4, respectively.

  In the piston rings of Examples 1 to 4 and Comparative Examples 2 and 3, a recess is formed so that the center of the recess is positioned at the center position of the axial width of the barrel width region, and the shape of the formed recess is hexagon. The length of the concave portion in the axial direction was 0.19 mm, the length of the concave portion in the circumferential direction was 0.16 mm, and the length in the concave portion radial direction was 10 μm. That is, in the piston rings of Examples 1 to 4 and Comparative Examples 2 and 3, the barrel width region is not penetrated by the concave portion (the concave portion non-forming region is present on all of the cutting surfaces in the ring axis direction of the barrel width region). ) A piston ring in which a recess is formed. In addition, the dimension of a recessed part is the value which measured and averaged five arbitrary recessed parts.

  Further, the piston ring of Comparative Example 4 is formed with a recess so that the center of the recess is positioned at the center position of the axial width of the barrel width region, and the shape of the formed recess is a hexagonal shape. The length in the direction was 1.30 mm, the length in the circumferential direction of the recess was 0.16 mm, and the length in the radial direction of the recess was 10 μm. That is, the piston ring of Comparative Example 4 is a piston ring in which a recess is formed so that the barrel width region penetrates through the recess.

(Measurement of area ratio of non-recessed area)
When the total area of the barrel width region before the formation of the recesses was taken as 100%, the area ratio of the non-recessed region where no recesses were formed in the barrel width region was measured. In addition, when the piston ring is mounted in the ring groove of the piston and the piston is incorporated in the cylinder, when the straight line passing through the center axis of the cylinder and the outer peripheral end of the joint is used as a reference line, the center axis is the center. No concave portion was formed in the barrel width region where the angle formed with the reference line was less than 5 °.

<Measurement results>
When the total area of the barrel width region before forming the recess is 100%, the area ratio of the non-recessed region where no recess is formed in the barrel width region is 90% for the piston ring of Comparative Example 2, and Example 1 The piston ring of Example 2 is 80%, the piston ring of Example 2 is 80%, the piston ring of Example 3 and Comparative Example 4 is 50%, the piston ring of Example 4 is 20%, and the piston ring of Comparative Example 3 is 15%. Met. In addition, the area ratio of the piston ring (piston ring in which the recessed part is not formed) of the comparative example 1 is 100%.

(Experiment 1)
<Measurement of reciprocating friction force>
The reciprocating frictional force (N) of the piston rings of Examples 1 to 4 and Comparative Examples 1 to 3 was measured using the apparatus shown in FIG. The measurement result of the reciprocating friction force is shown in FIG. In FIG. 12, the frictional force when the frictional force of the conventional piston ring in which the concave portion is not formed (the piston ring of Comparative Example 1 (the area ratio of the concave portion non-forming region is 100%)) is 1.00. Indicates the ratio. The rotational speed at the time of measurement of the reciprocating frictional force was 700 rpm, the piston ring ambient temperature was 80 ° C., and the supply oil was SAE viscosity 10W-30.

(Experiment 2)
<Blow-by gas test>
Subsequent to Experiment 1, a blow-by gas test was conducted with the piston ring mounted on the actual machine. Specifically, a diesel engine having a displacement of 3000 cc, a cylinder number of 4, a cylinder diameter of 95.4 mm, and a stroke of 104.9 mm was used. The rotation speed was 3600 rpm, and the water temperature was 80 ° C.

  Three piston rings are used, the first pressure ring is the piston ring of Example 3 and Comparative Example 4, the second pressure ring is a tapered undercut ring, the oil ring is a two-piece oil consisting of a coil expander and an oil ring body. A ring was used. FIG. 13 shows the blowby gas measurement results when the piston rings of Example 3 and Comparative Example 4 are used as the first pressure ring. FIG. 13 is a diagram showing a blow-by gas amount ratio when the blow-by gas amount of a conventional piston ring (the piston ring of Comparative Example 1) in which the concave portion is not formed is 1.

  As is apparent from FIG. 12, when the total area of the barrel width region before forming the recess is 100%, the area ratio of the recess-free region where no recess is formed in the barrel width region is 20% to 85%. It can be seen that the piston ring outside the range cannot exert the effect of reducing the frictional force.

  As is clear from FIG. 13, when the concave portion is formed so as to penetrate the barrel width region (when the concave portion non-forming region does not exist in all of the cut surfaces in the ring axis direction of the barrel width region) It turns out that the amount of blow-by gas will increase.

  From the results of Experiment 1 and Experiment 2, the area of the non-formed region 4 in which no recess is formed in the barrel width region is in the range of 20 to 85% when the total area of the barrel width region before forming the recess is 100%. It can be seen that it is preferable that a recess non-formation region exists in all of the cut surfaces in the ring axis direction of the barrel width region.

  Needless to say, the present invention is not limited to the above embodiments. For example, in the above embodiment, the blasting method is used for forming the recess, but the method is not limited to this, and a method using a corrosive solution may be used. Moreover, although the masking board was used in the said Example, it is not limited to this, You may use the masking sheet etc. which consist of resin.

DESCRIPTION OF SYMBOLS 2 ... Joint part 3 ... Recess 4

Claims (4)

A piston ring for an internal combustion engine that is mounted in a ring groove of a piston and slides with a cylinder liner or an inner wall surface of the cylinder,
Of the outer peripheral sliding surface of the piston ring, a plurality of minute recesses are formed in the barrel width region of the piston ring,
In the barrel width region, the area of the recess non-formation region where the recess is not formed is in a range of 20 to 85% when the total area of the barrel width region before the recess formation is 100%,
In all of the axial cut surfaces of the barrel width region, the concave portion non-formation region exists ,
In a state where the piston ring is mounted in the ring groove of the piston and the piston is incorporated in the cylinder,
When a straight line passing through the center axis of the cylinder and the outer peripheral end of the joint portion is used as a reference line, the barrel width region having an angle of less than 1 ° with the reference line around the center axis is The piston ring, wherein the recess is not formed .   The piston ring according to claim 1, wherein a hard coating is formed in the non-recessed region.   The piston ring according to claim 1 or 2, wherein the concave portion is formed so as not to straddle the lower end portion in the axial direction of the outer peripheral sliding surface.   4. The piston ring according to claim 3, wherein when the lower end portion of the piston ring is chamfered, the recess is formed so as not to straddle the chamfered portion.

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